Settled by Native Americans, this area was controlled by the Spanish Empire in the colonial era. In the 19th century, it was part of independent Mexico before the Mexican–American War and Gadsden Purchase.

Yuma County was one of four original Arizona counties created by the 1st Arizona Territorial Legislature. The original county seat was the city of La Paz; in 1871 it was moved to Arizona City, later renamed as Yuma in 1873.

NameNational LandmarkState LandmarkPoint of InterestOther Designation
Yuma Territorial Prison State Historic Park66000197N/AN/AState Park